Showing papers on "Earthquake resistant structures published in 1993"

Evaluation of site-dependent inelastic seismic design spectra

Abstract: Note: [163] Reference LCH-ARTICLE-1993-006View record in Web of Science Record created on 2007-04-24, modified on 2016-08-08

Applications of Viscoelastic Dampers to High‐Rise Buildings

Abstract: In this paper, the features of energy‐absorbing capacities of the viscoelastic damper and its effect on the structure during earthquakes are investigated. To clarify the behavior of the structure with added viscoelastic dampers, a new analytical model for the viscoelastic damper taking into consideration the earthquakelike loading and the temperature effect, in good agreement with experimental results, and an advanced finite element formulation for the viscoelastic damper are developed. The proposed method could be implemented easily in the finite element program. In this study the behavior of a 10‐story building equipped with viscoelastic dampers is examined while it is subjected to earthquake ground motions. Both analytical and experimental results show that the energy‐absorbing capacity of the viscoelastic damper decreases with increasing the ambient temperature. Numerical examples show that the responses, including displacements and stresses, of the high‐rise building to earthquake loadings are signif...

Full-Scale Implementation of Active Control. II: Installation and Performance

Abstract: An active bracing system has been designed, fabricated, and installed in a full-scale dedicated test structure in Tokyo, Japan, for structural-response control under seismic loads. In 1991, Soong et al. presented the design of the system along with simulation studies for the design earthquake. Presented in this paper, which is the second part of the sequence, are: (1) The description of the constructed system; and (2) the observed performance of the system under two actual earthquakes and other artificial loadings. Installation details of the system in the building structure are presented along with the selections for fail-safe shutdown operations in case of malfunctions. Also presented are the procedures for proper maintenance and self-testing, which ensure continuous control with minimal resources. The observed performance under artificial loadings and actual ground motions is compared with the estimated analytical response.

Behavior‐Based Method to Determine Design Shear in Earthquake‐Resistant Walls

Abstract: For earthquake-resistant design of reinforced concrete structures, the shear force for frame elements is established on the basis of the proportions and flexural strength of the element according to the American Concrete Institute standard 318-89 (1989), the Applied Technology Council Standard 3-06 (1989), and the Uniform Building Code, published in 1988. In this paper, a similar procedure is proposed for walls in medium-rise, reinforced concrete buildings. Results of small-scale dynamic tests of nine- and ten-story structures with walls are presented to provide data with which to evaluate methods of estimating base shear. Maximum base-shear response during these tests consistently exceeded limit analysis estimates calculated assuming a linearly varying acceleration distribution. If the observed force distribution is used in estimating base shear, the limit analysis estimates are acceptable. The need to take into account variations of inertial force distribution with base-motion intensity is supported by experimentally observed behavior, by modal analysis, and by nonlinear response-history analysis. After discussing other factors that influence maximum base shear, such as strain rate, strain hardening, and systematic experimental error, a design procedure for estimating shear demand for walls that reflects observed behavior is proposed.

Seismic Behavior of Moment‐Resisting Steel Frames: Analytical Study

Abstract: An analytical investigation into the seismic performance of steel momentresisting frames is presented. The International Conference of Building Officials (ICBO) provisions regarding seismic design ...

Seismic Behavior of Moment‐Resisting Steel Frames: Experimental Study

Abstract: An experimental evaluation of the seismic performance of momentresisting steel frames using weakcolumn strongbeam joints is described. This study is a continuation of an analytical investigation de...

Earthquake Analysis of Arch Dams. I: Dam‐Foundation Interaction

Abstract: A threedimensional boundary element technique for the earthquake analysis of arch dams is presented. The dam and the foundation rock are assumed to be viscoelastic domains, the latter being boundle...

Ductile Connections for Precast Concrete Frame Systems

Abstract: This paper describes a research program to investigate the behavior of ductile connections between precast beam-column elements. The objectives of the program are to provide rational design recommendations for engineers to detail precast frame connections for use in regions of seismic risk, and to develop analytical models, based on the behavioral information, to investigate the behavior of complete precast frame systems.

Seismic Response of Eccentrically Braced Tall Building

Abstract: Spectral analyses and system identification techniques are used to analyze a set of acceleration response records obtained during the October 17, 1989, Loma Prieta earthquake (\IM\ds\N = 71) from the 47-story, moment-resisting framed and eccentrically braced Embarcadero Building (EMB), located in San Francisco The EMB was constructed in 1979 based on the 1976 Uniform Building Code requirements and a design response spectra defined by two levels of earthquake performances The EMB is in the Lower Market area of San Frandicso, which is of great interest to the engineering community because of the area’s soft-soil characteristics that amplify ground motions originating at long distances, and because the Embarcadero Freeway (within 100 m of the building) suffered extensive damage during the earthquake and was razed in 1991 The first modal frequencies of the building at approximately 019 Hz (north-south) and 016 Hz (east-west) are identified The torsional response and rocking motions of the building are insignificant Discontinuity of stiffness and mass at the 40th-floor level causes significant response issues above that floor such as excessive drift ratios

Seismic Response of Composite Coupled Walls

Abstract: In many structures, height restrictions may require coupling of reinforced concrete walls by structural steel beams rather than conventional reinforced concrete beams. Through an experimental program, the seismic performance of this type of composite system was evaluated. The stiffness, energy dissipation capability, and hysteresis characteristics were studied. Simple design guidelines were developed. The experimental results were extended analytically to study the performance of a multistory structure with composite coupled walls.

Behavior of Externally Confined Concrete Columns

Abstract: This paper investigates the feasibility of strengthening of seismically deficient concrete columns with high-strength fiber composite straps. The concrete columns will be externally confined by wrapping thin glass-fiber-reinforced or carbon-fiber-reinforced straps around the column. The confinement provided by the straps will increase the stress and strain of concrete at failure and will increase its ductility. Moreover, the composite strap will prevent buckling of longitudinal bars and spalling of the shell and therefore will further increase the load carrying capacity of the column. Analytical models are developed and a seismically deficient parametric study is conducted to investigate the effectiveness of this technique for strengthening of concrete columns designed before the new seismic design provisions and codes were in place. The variables used in the parametric study include, concrete compressive strength, thickness of composite strap, clear spacing between composite straps and type of the composite strap, i.e., carbon fiber reinforced or glass fiber reinforced. The results indicate that external confinement provided by the composite straps significantly increases the strength and ductility of concrete columns.

Observed Response of Actively Controlled Structures

Abstract: Several active control systems have been developed, fabricated, and installed in full-scale structures and they have been subjected to actual wind forces and ground motions. The focus of this paper is on the observed response of one of these systems, an active bracing system, which was subjected to several recent earthquake episodes. It is shown that the active system performs, by and large, as expected, and its performance can be adequately predicted through simplified analytical and simulation procedures. The observed performance of the active bracing system is also compared with that of another system, an active mass damper, which was installed in the same structure.

Fluid Viscous Damper for Improving the Earthquake Resistance of Buildings

Abstract: Experimental results are presented which demonstrate that the use of fluid dampers as add-on devices in moment resisting frames substantially increases damping and reduces seismic story drifts, story shear forces, and floor accelerations.

Case study of the performance of prestressed concrete buildings during the 1985 mexico earthquake

Abstract: The overall effects of the 1985 Mexico earthquake on buildings are summarized, with special consideration of the performance of prestressed concrete buildings. Then, for five typical prestressed concrete buildings, results of analyses of the dynamic response, with due consideration of the soil-structure interaction, are presented. In general, the computed response of the buildings under the effect of a ground motion simulating the 1985 earthquake, corresponded reasonably well with their observed performance. Nevertheless, in some cases the analyses indicated that the buildings should have experinced a greater nonlinear behavior than the ones perceived from their level of damage. Some reasons for these differences are discussed. Recommendations on earthquake-resistant design of prestressed concrete buildings are given. The importance of providing lateral stiffness by shear walls or bracing, and of achieving ductility and continuity through mild steel reinforcement, is emphasized.

Seismic Performance Behavior of Precast Concrete Beam-Column Joints

Abstract: The experimental test program being conducted at the National Institute of Standards and Technology on 1/3-scale model precast concrete beam-to-column connections is summarized. The objective of the test program is to develop guidelines for an economical precast beam-to-column connection for regions of high seismicity. The test specimens were interior connections designed using the Uniform Building Code [ICBO, 1985 and 1988] criteria for seismic Zones 2 and 4 as guidelines. To date, fifteen specimens have been tested. Variables in the study include location of the post-tensioning steel, the use of post-tensioning bars versus prestressing strands, fully bonded versus partially bonded strands, and the combination of low strength steel and post-tensioning. Specimens were subjected to reversed cyclic loading according to a prescribed displacement history. Comparisons were made between the behavior of precast specimens and monolithic specimens. The comparisons were based on connection strength, connection ductility, and energy absorption characteristics.

Code Provisions for Unreinforced Masonry Bearing Wall Buildings in California

Abstract: Prior to the Long Beach earthquake of 1933, unreinforced masonry (URM) construction was usual in California, as it still is in many areas of the United States. The poor performance of these URM buildings in that earthquake led to State legislation regulating first new construction, then existing buildings. In addition, various cities have enacted seismic retrofit ordinances. Ultimately, seismic strengthening of existing URM bearing wall buildings was covered in a model building code, the Uniform Code for Building Conservation. This paper discusses the hazards presented by unreinforced masonry structures and presents a history of code development for their strengthening.

Seismic Performance of Joist‐Pocket Connections. II: Application

Abstract: The first of this 2-part paper described a technique for the examination of the seismic performance of joist and beam bearing connections in unreinforced masonry structures. In this second part, the approach is used to model a historic brick building that was shaken during the Loma Prieta earthquake in 1989. The paper discusses the effect of motion at the diaphragm-to-wall interface, as well as the importance of several parameters including the bearing length coefficient of friction, coefficient of restitution, and distance from end of joist to end of wall.

Earthquake - resistant design and construction of reinforced concrete buildings : The practice in Mexico after 1985

Abstract: The evolution of the design and construction practice of reinforced concrete buildings in Mexico is presented in terms of materials, structural systems, member design and reinforcement detailing. The main changes in the regulations and in the practice after 1985 are briefly described, along with the impact they have had on the characteristics of new building construction.

Report and Summary of ATC-31—Evaluation of the Performance of Seismically Retrofitted Buildings

Abstract: Structural and damage data for seismically retrofitted buildings affected by the October 1, 1987 Whittier Narrows and October 17, 1989 Loma Prieta, California earthquakes were collected and evaluated. The study confirmed that improved damage performance is achieved by thorough retrofitting of URM and tilt-up buildings and that arbitrary and incomplete retrofitting of these types of buildings does not significantly improve their performance when subjected to large earthquake ground motions.

Seismic capacity and failure modes of flat-bottom vertical tanks

Abstract: Flat‐bottom vertical storage tanks are vital components in nuclear power plant safety systems. Potential failure modes of such tanks due to earthquake ground motion and current methods available to evaluate the seismic capacities of tanks against these failure modes are identified. Substantial data on tank failure modes, seismic response, and seismic capacity are cited. These data are distinguished into three types: (1) Earthquake experience data from the performance of tanks in actual earthquakes; (2) test data from laboratory specimens or tanks in the field; and (3) analytical data from theoretical derivations or analyses. It is concluded that these data provide clear guidance on probable failure modes. Limited analyses have been performed to benchmark current seismic evaluation methods for tanks against test and earthquake experience data. In general, these studies demonstrate that current analytical evaluation methods provide sufficiently accurate means to predict the seismic capacities of flat‐bottom...

Design Criteria for Seismic Connections in Precast Concrete

Abstract: The seismic behavior of precast concrete is contrasted with that of cast-in-place and the conditions that precast must satisfy are reviewed. Design criteria and possible strategies for precast are presented.

Evaluation of US Seismic Code Provisions for Asymmetric-Plan Systems

Abstract: The effects of plan asymmetry on the earthquake response of code-designed, one-story systems are identified with the objective of evaluating how well these effects are represented by torsional provisions in US building codes. The earthquake-induced deformations and ductility demands on resisting elements of asymmetric-plan systems, are compared with their values if the system plan were symmetric. The presented results demonstrated that the design eccentricity in US building codes should be modified in order to achieve the desirable goal of similar ductility demands on asymmetric-plan and symmetric-plan systems. The design eccentricity should be defined differently depending on the design value of the reduction factor R.

Earthquake Prediction from the Viewpoint of Earthquake Engineering

Abstract: During the last decade there has been a considerable development and an intense activity of Earthquake Engineering all over the world. The general objective of that relatively new field of engineering is the study of the behaviour of buildings and other engineering structures (bridges: towers: reservoirs: etc.) under earthquake action. For the attainment of the above general objective, earthquake engineering follows two main directions: one towards the design of new earthquake resistant structures, and the other towards the protection and strengthening of existing structures. In following these two broad directions, earthquake engineering makes use of all available scientific knowledge that can be of help, not only from the related fields of structural and geotechnical engineering, but also from other fields like geology, geophysics and seismology. In this context, an interesting question arises whether prediction of earthquakes, a subject widely discussed at present, can be of use to earthquake engineering in its effort to achieve the above objectives.

Some proposals for implementation of the capacity design concept of eurocode 8 for steel structures

Abstract: In section 3 of eurocode 8-1 the concept of dissipative earthquake resistant structures is introduced. These dissipative structures are classified according to their seismic behaviour. Among them eccentrically braced multi-storey steel frame is recommended, where the inelastic energy dissipation is provided by bending and shear in a beam segment called a link. Because the link length is not specified in this code, this paper in the first part deals with link length fore wide flange cross sections of beams (and links) obtained at Berkeley after theoretical and experimental analysis of the various eccentric truss bracing systems and their elements. In order to be achieved the capacity design concept of the eurocode 8-1, in the second part this paper gives some detailing and proposals for connection design of centrically and eccentrically braced multi-storey steel frames subjected to earthquakes.

Steel Plate Energy Absorbers for Improved Earthquake Resistance

Abstract: This paper discusses results of an combined experimental and analytical investigation on seismic response of frame structures using welded steel triangular plates as added damping and stiffness device. The experimental responses of the proposed energy dissipating device are reviewed first. The effects of the ratio of the device stiffness to that of the bare frame and the ratio of the entire frame strength to that of the device are analyzed. Based on these studies, a design procedure useful to practicing engineers is developed.

Dynamic In-Plane Racking Tests of Curtain Wall Glass Components

Abstract: This paper is concerned with the seismic performance of 'architectural.' or 'non-structural' building elements such as glass elements in curtain wall systems. A pilot study was undertaken to investigate the dynamic racking performance of a 4.56 × 3.68 m section of curtain wall containing three, 1.52 × 1.84 m glass panels. Dynamic racking tests were performed totally in plane. Various types of glass specimens were tested, including annealed, heat strengthened and fully tempered glasses in monolithic and laminated configurations.

Quantitative controlling of structural response for base isolation and energy dissipation system

Abstract: This paper suggests the method of quantitative controlling of structural response for earthquake resistant structures with base isolation and energy dissipation system. This method is based on dynamic analysis, shaking table tests for a 1/4 scale steel frame model and a great number of low cycle fatigue failure tests for energy dissipating elements. A comparison between theoretical results and testing results is made. A set of calculation formulas for quantitative controlling of structural response of the structures with base isolation and energy dissipation system are derived and are able to be used in engineering design for earthquake resistant structures.